This application is a continuation-in-part of U.S. application Ser. No. 07/944,711 filed Sep. 11, 1992, still pending; which is a continuation of U.S. application Ser. No. 07/705,036 filed May 24, 1991, now abandoned.
The invention is directed to a magnetic latch. More specifically, the invention is directed to a magnetic latch which is stronger and more environmentally resistant than conventional magnetic latches.
Magnetic latches use magnetic force to hold two objects together. U.S. Pat. No. 4,021,891 issued to Morita on May 10, 1977, U.S. Pat. No. 4,453,294 issued to Morita on Jun. 12, 1984, U.S. Pat. No. 4,455,719 issued to Morita on Jun. 26, 1984, U.S. Pat. No. 4,700,436 issued to Morita on Oct. 20, 1987, U.S. Pat. No. 4,458,396 issued to Aoki on Jul. 10, 1984, U.S. Pat. No. 2,812,203 issued to Scholten on Nov. 5, 1957, U.S. Pat. No. 3,372,443 issued to Daddona on Mar. 12, 1968, and U.S. Pat. No. 3,618,174 issued to Schainholz on Nov. 9, 1971 disclose examples of conventional magnetic latches. U.S. Pat. No. 2,884,698 issued to Wursch on May 5, 1959 discloses a magnetic holding device for holding two pieces of metal together.
The latching strength of these conventional latches limits their utility. The latching strength of these latches may be increased by increasing the size of the latch. However, as the size of the latch increases, the usefulness of the latch in many applications decreases due to the bulkiness of the latch. In addition, larger latches are more expensive to manufacture, thereby reducing the cost effectiveness of larger latches.
Another disadvantage of these conventional magnetic latches is their unsuitability for use in a harsh environment. Generally, these conventional latches contain numerous cracks and crevices which collect caustic materials which corrode the latch parts and degrade its effectiveness. In a salt-air environment, the crevices in these conventional latches collect salt and other corrosive materials which ultimately corrode the latch parts. Thus, using these conventional latches to hold sails in place would be ineffective. Similar problems occur when using magnetic latches in a caustic chemical environment, for example, when using magnetic latches to seal protective clothing. Even the environment of a washing machine will cause most prior art magnetic latches to rust, limiting their usefulness on garments.
Many of the potential applications for magnetic latches require that the latch be resistive to lateral force. Therefore, magnetic attachment devices which do not resist lateral force, such as the device disclosed in the '698 patent cited above, are unsuitable for such applications.